Arboricultural Consultant

P.G. Biddle

Dr P.G. Biddle, O.B.E., M.A., D.Phil., F.Arbor.A.
Registered Consultant of the Arboricultural Association
Honorary Fellow, Insitute of Chartered Foresters

  Review - Rusell Grahame

Russell G Grahame, CEng, MICE, FIStructE, FCIArb

Review in The Structural Engineer 77 (6), 1999

The second volume of this work gives details of the drying of soil at various depths and at varying distances from trees over several years. The method used is given in some detail, and the abbreviations are to be found in this section. The effects of pruning have also been investigated and the results are included in this volume.

The first volume describes the various factors involved in the action of roots that cause damage to buildings. Eighteen of the twenty chapters cover soil, climate and weather, botany, factors affecting spread of roots, causes of damage, methods of investigation, remedial action, and prevention of damage. A further chapter deals with tree preservation orders and legal implications. The final chapter deals with the role of the professionals.

There are also twenty case studies: all of these being difficult cases where a degree of specialisation is required.

The coverage of these subjects is deep and thorough, while remaining clear and easy to read.

I cannot recall mention of Ward's finding, that a root can absorb moisture from a maximum of four feet beyond its tip (at least not in the place I expected to find it) but this apart, I can think of nothing which I feel was omitted, and I am fully in agreement with almost all that Dr. Biddle says. [The range of influence of roots is governed by the permeability of soil, and is considered on page 57 of Volume 1 - PGB]

I would take issue with his assertion that engineers tend to turn to underpinning too readily. In some seven hundred cases, I have used underpinning in about twenty, and most of the engineers I know in the field hold similar views.

The final chapter is of considerable interest and it is a great pity that it is likely to be read at drawing-board level rather than at board-of-directors level. It is hoped that Dr Biddle will expand this to a treatise, and may in future include the attitude of insurers who will pay thousands of pounds for underpinning but will make the insured pay for the much cheaper remedy of tree felling. He may also possibly mention the vicious circle of owners paranoid about their resale value, surveyors paranoid about their buyer clients and buyers with the same fears as vendors. Such a treatise from such a distinguished expert as Dr Biddle, directed at the corridors of power, could be the trigger for the changes in attitude which he advocates.

In conclusion, I would say that this work will be of great use to those engaged in designs where trees and buildings are to co-exist, in the diagnosis and repair of damage and it will be a very useful weapon to those doing battle with recalcitrant planners.